Display apparatuses have often to be adapted to display color adjustment. A typical display color adjustment includes adjustments of the color gamut and the white point. As known in the art, sRGB, AdobeRGB, NTSC (National Television System Committee) are typical display device specifications and these specifications individually specify the color gamut and the chromaticity coordinates of the white point. The color gamut is specified as the chromaticity coordinates of the respective elementary colors (R, G and B). The chromaticity coordinates of the elementary color points and white point of a display apparatus is preferably adjusted as specified by the specifications supported by the display apparatus.
One known approach to achieve color adjustment is to perform digital processing on image data of the image to be displayed. For example, Japanese Patent Application Publication No. P2008-40305A discloses a color adjustment technique which involves serially performing: a gamma conversion, an RGB-XYZ conversion, an XYZ-LMS conversion, a color shade adjustment, an LMS-XYZ conversion and an inverse gamma conversion.
Japanese Patent Application Publication No. P2008-141723A discloses a technique for converting YCbCr data into Adobe RGB data through an YCbCr-RGB conversion and an RGB-RGB conversion. This patent document discloses the RGB-RGB conversion involves a gamma conversion, a matric operation and an inverse gamma conversion.
Japanese Patent Application Publication No. P2002-116750A discloses a technique for achieving a precise color correction with a simple circuit configuration. In the technique disclosed in this patent document, the color correction is achieved by serially performing a gamma conversion with an LUT (lookup table), a matrix operation and an inverse gamma conversion with an LUT.
International Publication No. WO2004/070699A discloses a technique which involves: dividing the color gamut of a display device into a plurality of regions with segments which connect the chromaticity coordinate points corresponding to the white color to those corresponding to the elementary color points and the complementary color points; determining which of the regions the chromaticity coordinate point corresponding to the input signal is positioned in; and correcting the RGB values of the input signal on the basis of suitable RGB correction values corresponding to the chromaticity coordinate points corresponding to the three vertices of the region in which the chromaticity coordinate point corresponding to the input signal is positioned. This patent document also refers to calculation of the RGB correction values for the case when the display panel has gamma property proportional to the 2.2th power.
However, there is room for improving the preciseness of color adjustment in the above-described techniques.